1. Field of the Invention
This invention relates to an apparatus for measuring the internal dimensions of an enclosure and more specifically to an apparatus including one or more transducers.
2. Description of the Prior Art
In many industries such as the oil industry, it is important to determine the physical integrity of certain enclosures. In the oil industry, piping is an important conduit for the transportation of oil. The physical integrity of the pipe itself is very important. To that end, tools have been used to determine the internal physical integrity of pipes by making measurements along several locations of the internal circumference of the internal diameter of the pipe.
Problems have occurred with these types of measurement tools because of the extreme environment to which these tools are exposed within these pipes. Since, in oil wells, the pipes can be as deep as two miles, these measuring tools may be exposed to extreme heat and high pressure.
One tool, used for determining the internal diameter of a pipe along several points of circumference, includes several feeler arms attached to a housing. The feeler arms extend out from the tool housing and engage the interior surface of the pipe along several points. The tool housing is moved through the pipe along the axis of the pipe. The feeler arms are rotatably mounted within the tool housing such that the feeler arm position relative to the internal surface of the pipe is translated into a vertical up and down motion within the tool housing relative to the pipe axis. Previously, this up and down motion was used to turn a shaft connected to a potentiometer in the tool housing. Commonly, the gearing arrangement is set up such that the tool housing includes two potentiometers, one to record the maximum position of the feeler arms and the other to record the minimum position. Problems occur with the tool because these potentiometers are unable to function consistently when exposed to high pressures and high temperatures. The high temperature causes the potentiometers to drift and the high pressure can cause seals to break connecting the potentiometer shafts to the mechanical mechanisms of the feeler arms resulting in physical damage to the potentiometers.
The application of linear displacement transducers to the above problem was considered. One such linear displacement transducer is the type produced by Temposonics Incorporated and measures linear displacement by the use of magnetostriction of magnets on a linear wire combined with a pulse generator and a sensing circuit for sensing the return of the pulse resulting from the pulse interaction of the magnetic field through the wire at the point of the magnet location. Unfortunately, this linear wire expands under high temperature and will also give inconsistent readings for varied temperature environments.
The object of the present invention is to provide a caliper tool for measuring the internal integrity of an enclosure consistently through a broad temperature range.
It is a further object of the present invention to provide a magnetorestrictive displacement transducer that compensates for variations in temperature.